Control instrument



-Aug. 5, 1941. R. ULLMAN 2,251,535

CONTROL INSTRUMENT Filed June 14, 1938 HHHHH INVEN TOR. {)Y ULLMAN BYHWA TTORNEY Patented Aug. 5, 1941 I I CONTROL INSTRUMENT Roy Ullman,ltodyn, Pat, aasignor to The Brown Instrument Company, Philadelphia, Pa,a corporation of Pennsylvania Application June 14,1938, SerialNo.213,620

' comma, (01. 236-74) The general object of the present invention is toprovide improvements in control instruments of the type including ameasuring element deflecting in accordance with a measurable controlquantity, and a relay mechanism or power device through which saidmeasuring element affects adjustments of a control device which are notpractically obtainable through direct connection of the measuringelement and control device. More specifically, the object of myinvention is to provide an instrument of the type mentioned withmechanical relay provisions of novel construction to establish arelation between the movements of the deflecting element and controldevice, which is desirable in respect to both the magnitude and timingof said variations.

My improved instrument is adapted to a wide range of uses, inasmuch asits deflecting element may be responsive to, and by its movements be, ameasure of temperature or pressure, or other physical condition, whichby changes gives rise to variations in a measurable force resulting incontrol actions selectively dependent upon such variations.

In a preferred form of my invention, a variation in the condition beingmeasured determines the setting of a directional switch in the relay.Another switch in series with the directional switch regulates theamount of energization of a motor in the control device. The secondswitch may be closed for either a predetermined time each cycle or for avariable time depending upon the variation of the measured conditionfrom a desired value.

a The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, its advantages and specific objects obtained with its use,reference should be had to the accompanying drawing and descriptivematter in which I have illustrated and described a preferred embodimentof the invention.

Fig. 1 is a view including an elevation of the,

relay, and including a diagrammatic representation of furnace controlprovisions cooperating with the relay to maintain predetermined furnaceconditions;

Fig. 2 is a view of a modified relay; and

Fig. 3 is a view showing various of the parts of the modification ofFig. 2 disassembled.

In the embodiment of the invention shown in Fig. 1, my improved controlinstrument comprises mechanism which may be located in an ordinaryinstrument casing. The instrument is employed to adjust a fluid supplyvalve l of a furnace or heater 2 as required to maintain a predeterminedfurnace temperature to which a device 3 is responsive. As shown, thedevice I is the bulb of a fluid pressure thermometer, the pressure ofwhich istransmitted by a tube 4 to the stationary end of a Bourdon tube5 that adlusts the position of a contact member 6 pivoted at I. As thetemperature in the furnace varies, the tube 5 expands or contracts toraise or lower the contact member 6 which forms part of a proportioningsystem to be later described.

I A reversible motor 8 comprising two reversely wound fields l and i isconnected to the valve l to open or close it, depending upon thevariations in temperature of the furnace 2. Both of the motor fiels 8and H) are connected by a lead H to one side L' of an alternatingcurrent supply system of customary commercial voltage for lighting andpower purposes. The other side of the line L goes through conductor l2to a timing mercury switch I3 and from there through line H to onecontact of each end of direction controlling mercury switch Hi. Theother contact of the left end of switch l goes through conductor 16 tofield .9 while the second contact of the right end of switch l5 goesthrough conductor H to field III.

The timing switch I3 is mounted for tilting movement on a combinedbracket therefor and lever it that is pivoted at I! and has a normalgravitational bias in a counterclockwise direction. The other end of thelever l8 has a roller 20 thereon that bears against a constantlyrotating cam 2| which serves to control the tilt-. ing movement of thelever is and therefore the opening and closing of the switch lit. Thecam 2| is made up of two concentric parts 21a and 2), one of which isfastened to, and the other of which is rotatable on, a shaft 22. Thepart 2lb, which is rotatable on shaft 22, has a series of holes in it,through any one of which a screw 23 may be inserted and screwed into ahole in part 2la fastened to the shaft. By this means the percentage ofhigh and low portion of the cam may be varied. The shaft 22 is driventhrough gearing 24 from any suitable constant speed motor (not shown).

The direction controlling switch i5 is mounted for tilting movement onan abutment member 25 that is pivoted at 28 and is biased in a clockwisedirection by a spring 21. This abutment member has an arm 28 on thelower end of which is a roller 2! bearing on a cam 30 fixed to shaft 22in a definite angular relation to part 2| a of cam 2|. The left end ofabutment member has adjustably attached to it another abutment member3|. As the cam rotates with shaft 22, it periodically moves the abutmentmember 25 and its attached switch |5 in a counter-clockwise directionand then permits them to move clockwise under the bias of spring 21 to aposition depending upon the then value of the condition being measured.

The point at which the clockwise movement of member 25 is terminateddepends upon the position of an arm 34 of a relay 35 which is responsiveto changes in the value of the condition. This arm can engage eitheredge 33 or edge 32 of the abutment members 25 and 3|, or can miss thementirely, and thus cause the contacts at one end or the other of switch|5 or neither set of contacts to be closed. The relay 35 comprises atilting'member 36 that is fastened to arm 34 and is pivoted around a pin31. Member 36 has formed on each of its ends cores 38 and 39 that arearranged in inductive relation with coils 40 and 4| respectively. Aspring 42 is fastened to the frame of the relay 35 and the member 36 tolightly normally bias this member and arm 34 into their mid-position.

Angular adjustment of contact member 6 by the Bourdon tube 5 controlsthe adjustment of the heater supply valve and gives the latteradjustment movements in a direction corresponding to the adjustment ofcontact member 6. The adjusting means forms part of the controlinstrument and comprises an electrical resistance 43 so disposed that asthe contact 6 moves through its range of oscillation, it will engage theresistance 43 at different points along its length. Conductors 44 and 45are connected to the ends of resistance 43, and a conductor 46 isconnected at'lto the end of contact member 6. The conductors 44 and 45are connected to the ends of a resistance 41 which is engaged by acontact member 48 that is movable along the resistance 41 in a mannersimilar to the movement of member 6 along resistance 43. The resistances43 and, 41, conductors 44 and 45, and contact members 6 and 48 formparts of a Wheatstone bridge arrangement which is energized by atransformer 49, the terminals of the primary windings of thattransformer being connected by conductors 50 and 5| to conductors 44 and45 respectively. The terminals of the secondary winding of transformer49 are connected to the A. C. supply L and L The relay 35 forms part ofthe proportioning means and is connected to the Wheatstone bridgearrangement in the following manner. The con ductor 46, extending fromjunction 1, forms a common lead for each coil 40 and 4| while coil 40 isconnected by conductor 52 to conductor 5| and conductor 45, and coil 4|is connected by conductor 53 to conductor 50 and conductor 44.

In any condition of stable operation, the currents flowing through relaycoils 40 and 4| will be equal, and the armatures 38 and 39, member 35,and arm 34 will be in their neutral position so that upon an upwardmovement of abutment 25, arm 34 will engage edge 32. Any deflection ofcontact member 6 along resistance 43 will make the currents flowingthrough coils 40 and 4| unequal, and will result in a deflection of arm34 from its mid-position. For example, on a deflection of contact member6 downwardly, corresponding to a decrease in the temperature of the bulb3 below its normal value, the current aasrsss flowing through relay coil4| will be increased relatively to current flow through the coil 40 Inconsequence, the armature 39 will be moved downwardly, bringing arm 34to the left of the path of edge 32 upon its upward movement. If, on theother hand, the temperature of the bulb 3 increases above its normalvalue, the contact member 6 will be lifted upwardly along resistance 43,and thereby cause an increase in the current flowing in coil 40 relativeto the current flow in coil 4|. This will cause the armature 38 to bemoved downwardly and arm 34 to be moved into the path of edge 33.

As cams 2| and 30 rotate in a counter-clockwise direction, the lever I8and abutment 25 are periodically moved around their pivots to adjusttheir respective switches. The cams are arranged relative to each otherso that during their rotation, abutment 25 will be permitted by cam 30to turn clockwise under the bias of spring 21 while the roller 20 oflever I8 is still in engagement with the high portion of cam 2|, andconsequently the switch I3 is in it open position. As the left endabutment 25 rises, it will or will not be stopped at some point in itsmovement by engagement of edge 32 or 33 with arm 34, depending upon theposition of the latter. As shown in the drawing, the arm 34 has engagededge 32 to stop the abutment 25 in a horizontal position, and thereforeprevent either of the pairs of contacts, at the ends of switch I5, fromclosing. Continued rotation of the cams will bring the low portion ofcam 2| over roller 20 to permit lever II to tilt to close switch |3.Inasmuch as neither pair of contacts in switch |5 is closed, the motor 8will not be energized. The switch |3 will remain closed a predeterminedtime depending upon the relative positions of parts 2|a and 2|b of cam2| and the speed of rotation of the cams.

If the temperature of bulb 3 increases, on the following cycle the arm34 will be in the path of edge 33, in a manner above described, as theleft end of abutment 25 rises, and the abutment will be stopped in sucha position that the pair of contacts at the left end of switch |5 willbe closed. Subsequently, in the cycle upon the closure of switch |3 bycam 2|, the field 9 of motor 8 will be energized to rotate the motor insuch a direction that valve I will be closed to supply less fuel to theheater 2. This same rotation' of the motor will also act to shiftcontact member 48 downwardly along resistance 41. The resultant movementof the contact 48 tends to make the sum of the portion of resistance 41between the contact 48 and the conductor 45, and in the portion of theresistance 43 between contact 8 and the conductor 44, equal to the sumof the other portions of the resistances 43 and 41; whereupon thecurrents flowing through the relay coils 4| and 40 will be made morenearly equal, and the arm 34 will be returned toward its mid-position.Any adjustment of the contact 6 in either direction thus produces acorresponding adjustment of the valve and contact 48 in one direction orthe other through the relay 35 and the cam and switch arrangement. Theseadjustments continue in steps until such time as the temperature of thebulb 3 has re turned to its normal value. At this time, the currentflowing in coils 40 and 4| will be equal. and the arm 34 will again moveto its midpositi-.n.

Upon a decrease in the temperature in bulb 3, the arm 34 will be movedto the left, and when autment member 25 rises, neither of the edges I or33 will be engaged by it. Therefore, the butment member 25 can riseuntil the pair of mta'cts in the right end of switch I are closed. his,when switch I3 is later closed, will energize eld ll) of motor 8 to runit in a direction to open alve I going to furnace 2 and also to move theontact 48 upwardly along resistance 41.

Continued rotation of cams 2| and 38 will rst open switch l3 and thenmove abutment iember in a counterclockwise direction to )wer its edges32 and 33 in preparation for anther cycle.

In the form of the invention. disclosed in Fig. the motor 8, if it isenergized due to a devialon of the measured temperature from a desired'alue, is energized to run a predetermined period f time regardless ofthe amount of variation in he temperature. lisclosed in Figs. 2 and 3differs from the above orm in that the motor 8 is run to adjust the'alve an amount proportional to the deviation vi the temperature from adesired value. This 'orm of the invention is identical to Fig. l in L11respects but the details of the mechanical 'elay. There is provided aprimary abutment nember that determines the direction of rotation )fmotor 8 which is responsive to .the position )f arm 34, and there isprovided a secondary ibutm'ent member, also responsive to the posi- ;ionof arm 34, to determine the amount of time ;he motor 8 will-beenergized.

To the above'end there is provided-a shaft 55 upon which is pivoted aprimary abutment memoer 56 which carries the double throw switch l5.

This member 56 has a fiat edge 56a at its left end and is biased in aclockwise direction by spring 51. Also pivoted on shaft 55,and in frontof member 56, is a secondary abutment member 58 that has formed thereona bent- The form of the invention over projection 59 which normally-.overlies the upper edge of member 56. The left end of member 58 isformed with an upwardly extending,

opposed series of steps 68 that are individually adapted to be engagedby arm 34 on their up ward movement. The step that is engaged dependsupon the amount and direction of deviation of the arm 34. In front ofmember 58, and also pivotally mounted on shaft 55, is a bracket 6| forsupporting switch I3, the bracket being formed on its left edge with abrake-surface 62. Aicatch mechanism for moving bracket 6| with member 58on its upward movement'is provided and consists of a lever 63 movablearound shaft 55 to the outer end of which is pivoted at 64 abrake-member 65. The brake-member is provided between its ends with apin 66 and at its outer end with a roller 61 that underlies member 58.Upward movement of the secondary abutment mem r 58 and brake-member 65is accomplished by ell-crank lever 68, pivoted on shaft 55, and biasedin a clockwise direction by spring 69. This bell-crank has a notch 18formed in its outer end that is adapted to engage pin 66, and isprovided between its ends with an overhanging projection '1I that isadapted to engage the top surface of member 58. A cam 12 is mounted onshaft 13, driven at a constant'speed by any suitable source of power,and is used to move the various parts in a counter-clockwise directionagainst the bias of their respective springs.

In the operation of this form of the invention as the temperature of thebulb 3 varies, the

contact member 6 will be moved along resistance43 and, through the abovedescribed circuits, will cause arm 34 to be moved either to the right orto the left, depending upon whether the temperature change was adecrease or an increase. Upon rotation of cam 12, member 56 followed, asshown in Fig. 2, by member 58 will be moved in a clockwise direction byspring 51. If the arm 34 is in its mid-position, or to the left thereof,the edge 56a of member 56 will not engage arm 34 .but will continue torise until the contacts in the right end of switch ii are closed. If thearm 34 is in its mid-position, indicating normal temperature of theheater, the topmost step 600. of member 58 will engage the arm, and thesecondary member 58 will be stopped. In this position of member 58, thebracket 6| and switch l3, moving therewith, are at such an angle thatthe switch is just about to close.

Continued rotation of cam 12 will let the bellcrank 68 continue to moveunder the bias of its spring 63 so that the notch 18 encirclingpin 66will exert an upward force thereon. Since member 58 can no longer moveupward, the roller 61 on brake 65 will act as a fulcrum for the brake sothat as pin 66 moves up, the roller 61 will move to the right, and brake65 and lever 63 will move relative to each other to lift the right endof brake 65 from brake-surface 62 of bracket 6|. The bracket 6| andswitch l3 will then fall colunter-clockwise under a gravitational biasuntil they engage stop 14. In this manner, even though a pair ofcontacts in switch l5 are closed, the motor 8 is not energized sinceswitch l3 was dropped before it was closed. Continued rotation of cam 12will cause it to engage roller 15 on bell-crank 68 to move thebell-crank clockwise so that clockwise movement of notch 16 will restorelever 68 and brake 65 to their initial positions, andprojection 1| willengage the top edge of member 58 to move it downwardly.

As member 58 moves down, the projection 58 will engage the top edge ofmember 56 to move it, along with the other parts, downwardly to permitarm 34 to swing free. I

If the temperature of the heater and,. therefore, the bulb 3 isincreased, the arm 34, as above described, will be moved to the right.Upon clockwise movement of the member 56, edge 56a will then engage arm34 and .be stopped in such a position that the pair of contacts in theleft end of switch i5 will remain closed, thus determining which fieldof the motor 8 will be energized. Continued clockwise movement ofbell-crank 68 by its spring 68 will, by means of n'otch 10, pin 66,brake 65 and roller 61, lift member 58 until one of the right-hand steps68 engages arm 34, the particular step depending upon the amount ofdeviation of the arm. When the member 58, during its clockwise movement,moves just beyond where it would go if arm 34 was in mid-position, theswitch |3 will be closed to energize the motor 8, in this condition ofthe temperature, through field 8. This energization will continue untllmember 58 is stopped by engagement of one of the steps 68 and arm 34,and the continued upward movement of pin 66 will remove brake 65 frombrake-surface 63 so which the right-hand contacts of switch Hi canclose. Upward movement of member 58 is stopped when one of the left handsteps 60 engages arm 34, the deviation of the arm 34 determining whichstep and therefore the amount of time the motor 8 will be energizedbefore the switch i3 is released so it can drop and open the motorcircuit.

From the above detailed description of my invention, it will be seenthat I have provided a mechanical relay that is adapted to be used incombination with an electrical proportioning systern to vary the fuelsupply to a heater, in order to maintain the temperature of the heaterconstant. This combination of a proportioning systern and mechanicalrelay for energizing a motor is very useful, as well as being simple andaccurate. The special advantages of this combination include a compactarrangement of parts that are easily assembled in a small space and thatdo not require any external connections but an ordinary A. C. electricsupply line that is obtainable at practically every locality.

It will also be apparent that the type of relay disclosed may be usedwith any self-balancing measuring system and is not necessarily limitedto the proportioning system with which it is disclosed by way ofexample. For example, the pointer 34 may be movable in response togalvanometer unbalance in an ordinary self-balancing potentiometercircuit.

While in accordance with the provisions of the statutes, I haveillustrated and described the best form of my invention now known to me,it will be apparent to those skilled in the art that changes may be madein the form of the apparatus disclosed without departing from the spiritof my invention as set forth in the appended claims, and that certainfeatures of my invention may sometimes be used to advantage without acorresponding use of other features.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In a control instrument the combination with a reversible motordriving means to adjust the value of a controlled condition, a firstswitch for determining the direction of rotation of said motor, a secondenergization controlling switch in circuit with said first switch, abalanced electric circuit, means responsive to variations in saidcontrolled condition for unbalancing said circuit, and means forperiodically closing said first switch in accordance with said variationand for thereafter periodically closing said second switch to energizesaid motor.

2. In a control instrument, a double throw switch normally movable inone direction, a cam for periodically moving said switch in anotherdirection, means adapted to interrupt the movement of said switch insaid one direction, said means being responsive to variations in avariable condition, a second energization controlling switch, a cam forperiodically tilting said second switch, said cams being so timed thatthe second.

single throw energization controlling switch in circuit with saidfirst-named switch, means to close and open the second mentioned switchbetween the operations of the first mentioned switch, a reversible motoradapted to be energized when said switches are closed, a balancedelectrical circuit, a member responsive to the variation of a conditionto unbalance said circuit, means in said circuit determining the throwof said first switch in accordance with said unbalance, and meansoperated by said motor, when energized, to rebalance said circuit.

4. In a control instrument, a reversible electric motor, a double throwswitch for determining the direction of rotation of said motor, a singlethrow switch in circuit therewith for determining the amount of timesaid motor is energized, a constantly rotating cam for actuating eachswitch, said cams being timed to actuate the single throw switch afterthe double throw switch, a member responsive to variations in acondition, and means regulated by said member for determining thedirection of throw of said first switch, whereby said motor will beenergized to run in a direction depending upon the variation in saidcondition.

5. In a control instrument, a first pivoted lever having a switchthereon, a second pivoted lever, a second switch movable therewith, ameans responsive to the variations of a condition in the path ofmovement of said second lever and adapted to be in the path of movementof said first lever or not in accordance with said variations, means toperiodically move said first lever and then said second lever to closesaid switches, movement of said first lever being dominated by saidfirst-named means, and a reversible motor energized by the closing ofsaid switches, to adjust said condition.

6. In a control instrument, a member adjusted into different positionsin accordance with variations in a control condition, a device forregulating said condition, a motor for adjusting said device, a firstdirection controlling switch for said motor, a second time ofenergization controlling switch for said motor, separate means carryingsaid switches, means for periodically moving said carrying means intoengagement with said member, the carrying means for the first switchbeing in advance of the carrying means for the second switch whereby todetermine the setting of said switches in accordance with the positionof said member to determine the direction and time of energization ofsaid motor.

7. In a control instrument, a member movable in accordance withvariations in a control condition, a movable lever having a plurality ofedges thereon, a direction controlling switch attached to said lever,means for periodically moving said lever toward and from said member,said member engaging one of said edges or not dependent upon theposition thereof to thereby set said switch, a motor, saiddirection-controlling switch being in the motor circuit, a second switchin circuit with said direction-controlling switch and said motor andmeans for periodically closing said second switch to energize said motorafter said direction controlling switch has been set.

8. In a control instrument, a motor, means for periodically energizingsaid motor comprising a first direction controlling switch, and a secondtime of energization controlling switch, a member positioned inaccordance with variations in a condition to be controlled, means forperiodically positioning said first switch in accordance with theposition said member and means for thereafter periodically closing saidsecond switch to thereby energize said motor in accordance with theposition of said member.

9. In a control instrument, the combination 5 with an element movable inaccordance with variations in a condition to be controlled, 9. balancedelectrical circuit, means responsive to variations in said condition tounbalance said circuit, a reversible motor to rebalance said circuit, 10

